Frequently Asked Questions

UBC Mathematics: MathNet FAQ [Browser Busy]

Question: How do I handle complaints from Firefox that another browser is running?
Author: Joseph Tam
Date: Dec. 07, 2010

Quick Fix

This usually only happens on the Unix (Solaris, Linux, etc.) version of
Firefox. For a quick and fast fix, run this command on the same workstation
you usually run Firefox on:

KillMyFirefox

For a more detailed explanation and details on what the script is doing,
please read the next section.

Technical Details

A browser will refuse to start if it believes another instance of
itself is running elsewhere. It does this to ensure the consistency
of its data (bookmarks, browsing history, etc.) by making sure another
browser is not abot to modify it at the same time.

A browser checks the existence of a lock file created by another
browser. Problems arise if the original browser that created the lock
file crashes or ends abnormally without removing its lock file, thus
preventing new browser instances from starting up.

Firefox's lock files are typically located in one of several locations:

In the example, the lock is owned by a browser running at host address
12.34.56.78 with process id 9876.

The first step to unlocking the browser is to check whether another
browser is really holding a lock. It may be running on another terminal
or on another workstation; closing that application will release the
lock.

> ssh smith@12.34.56.78
> ps -p 9876

If this process exists (and you're not in a position to manually
close the application), you can kill the process by using the command

> kill 9876
# ... or in extreme cases ...
> kill -9 9876

Once you're sure browser is gone, you can remove the lock file if it exists: